1. Field of the Invention
The present invention relates to a half-pixel processing apparatus of a macroblock for motion compensating a moving image, and more particularly, to a half-pixel processing apparatus of a macroblock for motion compensating a bidirectionally-predictive coded picture (B-picture) which performs a motion compensation operation with past and/or future reference pictures.
2. Description of the Related Art
When encoding a motion image signal into digital data and processing the digital data, the amount of data is largely increased when an image signal is moving. To solve this data increase problem, a compression technology of compressing motion image data has been developed which removes redundant data of the motion image signal.
To effectively compress motion image data, three types of pictures such as an intra-coded picture (I-picture), a predictive-coded picture (P-picture) and a bi-directionally-predictive-coded picture (B-picture) are defined in the Moving Picture Experts Group (MPEG) standard. The I-picture is defined as being encoded without reference to the other pictures, the P-picture is defined as being encoded using motion compensated prediction from a past I-picture or P-picture, and the B-picture is defined as being encoded using motion compensated prediction from a past and/or future I-picture of P-picture.
The MPEG-2 standard adopts a half-pixel processing method for a more accurate motion compensation operation. The half-pixel processing method obtains interpixel data by averaging data of horizontally and/or vertically neighboring pixels. A conventional half-pixel processing method reads vertically neighboring 16 pixels per macroblock at a time for horizontal half-pixel processing, to average horizontally neighboring two pixels, and reads horizontally neighboring 16 pixels per macroblock at a time for vertical half-pixel processing, to average vertically neighboring two pixels. Since screens of pictures which are located in the front area or the rear area thereof for a motion compensation of the B-picture, a memory for separately storing data of the pixels of the previous line is required to process a half-pixel of a macroblock. Also, it is impossible to successively output data.